1. Field of the Invention
The present invention relates in general to controllers for an automotive air conditioner, and more particularly to damper door controllers which adjust positions of various damper doors installed in a cooler/heater unit of the automotive air conditioner.
2. Description of the Prior Art
Usually, various damper doors are installed in a cooler/heater unit of an automotive air conditioner for controlling the temperature of air blown into various given portions of a motor vehicle, which are, for example, an upper portion of a passenger room, a lower portion of the passenger room, an inside space facing a windshield, etc.,. In fact, due to pivot operation of the damper doors, various modes are provided by the cooler/heater unit, which are, for example, a ventilation mode wherein conditioned air is blown to the upper portion of the passenger room, a foot mode wherein the air is blown to the lower portion of the passenger room, a bilevel mode wherein the air is blown to both the upper and lower portions of the passenger room and a defrost mode wherein the air is blown against an inside surface of the windshield to defrost the same.
Usually, the damper doors are remotely controlled through a link mechanism by a mode selection knob which is carried on a knob holder unit arranged on an instrument panel of the motor vehicle. That is, by manipulating the mode selection knob, the damper doors of the cooler/heater unit are pivoted to selected positions to provide the unit with one of the above-mentioned modes. In addition to the mode selection knob, the knob holder unit has further a temperature control knob by which an open degree of one damper door (viz., air mixing door) is controlled for adjusting the temperature of air blown to the passenger room, a fan speed control knob by which the amount of air fed to the passenger room is controlled, and an air conditioner switch by which a cooling cycle of the air conditioner is turned ON or OFF.
To transmit the movement of the mode selection knob to the damper doors through the link mechanism, a cable type movement transmitting mechanism is hitherto employed wherein a control cable extends from the mode selection knob to the link mechanism, which is shown in, for example, Japanese Utility Mode First Provisional Publication 1-175410 and 2-104415. In the cable type movement transmitting mechanism shown in these publications, a rotary mode selection knob is used, so that rotating movement of the mode selection knob induces movement of the control cable and the link mechanism for pivoting the damper doors to desired positions. A rack-and-pinion unit is employed for transmitting the rotating movement of the rotary mode selection knob to the control cable. That is, a pinion is coaxially connected to the rotary mode selection knob to rotate therewith and a rack member is connected to a leading end of the control cable. The control cable is slidably received in an elongate plastic sleeve which has a leading end clamped to a base plate of the knob holder unit.
However, due to its inherent construction, the cable type movement transmitting mechanism shown by the above-mentioned publications has failed to provide the users with satisfaction. That is, in the mechanism, it is inevitably necessary to have the rack member projected from the plastic sleeve by a degree corresponding to a reciprocating movement thereof induced by the rotating movement of the rotary mode selection knob. This means that for achieving a smoothed movement of the control cable in the plastic sleeve the clamped end of the plastic sleeve should be so oriented that the opening thereof faces against the direction of the way along which the rack member moves. More specifically, a certain length of an end portion of the plastic sleeve including the clamped end should extend straight along with an extension of the way along which the rack member moves. However, such straight extension of the sleeve causes a too long construction of the movement transmitting mechanism. Furthermore, such straight extension induces a need of providing the sleeve with a sharply curved portion particularly when the transmitting mechanism is installed in a limited space of a motor vehicle. As is easily known, presence of such sharply curved portion on the sleeve increases the sliding friction of the control cable in the sleeve, which obstructs a smoothed movement transmission from the rotary mode selection knob to the damper doors.